The field of the disclosure relates generally to components having an internal passage defined therein, and more particularly to forming internal passages that include interior passage features.
Some components require an internal passage to be defined therein, for example, in order to perform an intended function. For example, but not by way of limitation, some components, such as hot gas path components of gas turbines, are subjected to high temperatures. At least some such components have internal passages defined therein to receive a flow of a cooling fluid, such that the components are better able to withstand the high temperatures. For another example, but not by way of limitation, some components are subjected to friction at an interface with another component. At least some such components have internal passages defined therein to receive a flow of a lubricant to facilitate reducing the friction.
Moreover, a performance of at least some such internal passages is improved by the addition of interior passage features, that is, structural features that extend within the passage and alter fluid flow within the passage, as compared to fluid flow within an otherwise similar, but substantially smooth-walled, passage. As just one example, interior passage features that extend inward from a wall of such passages may be used to turbulate a flow of a cooling fluid flowed through the passage, such that a thermal boundary layer proximate the passage wall is disrupted and heat transfer efficiency is improved.
At least some known components having an internal passage defined therein are formed in a mold, with a core of ceramic material extending within the mold cavity at a location selected for the internal passage. After a molten metal alloy is introduced into the mold cavity around the ceramic core and cooled to form the component, the ceramic core is removed, such as by chemical leaching, to form the internal passage. One known approach to creating interior passage features is to form complementary features on a surface of the ceramic core prior to forming the component in the mold. However, at least some known ceramic cores are fragile, resulting in cores that are difficult and expensive to produce and handle without damage. In particular, the addition of complementary surface features on the core introduces stress concentrations that increase a risk of cracking of the ceramic core. Another approach is to add the interior passage features after the component is formed in the mold, for example, by using an electrochemical process to shape the passage wall. However, at least some such post-forming processes are relatively time-consuming and expensive. Moreover, with respect to both known approaches, a geometrical complexity of the interior passage features that can be formed is substantially limited.